Inorganic nanofibrous membranes have recently attracted increasing attention in the fields of catalysis, adsorption, fuel cells, sensors and filtration.1-6 In view of their mechanical resistance and excellent performance in the removal of pollutants, inorganic nanofibrous membranes with different structures and properties have been successfully applied for water purification.5-7 Successful application of inorganic membranes in water purification will depend upon the ability to prepare membranes with the desired pore size,8 which would affect the selectivity and permeability of the membrane.
Previous studies have shown that various techniques such as self-assembly, electrospinning and selective etching of templates can be used to synthesize inorganic nanofibrous membranes.6,7,9,10 Unfortunately, these techniques for membrane synthesis suffer from poor selectivity and permeability, complicated technical requirements and high operational costs, thus severely restricting water purification applications.6,11 As the final step during the preparation of a traditional inorganic membrane, calcination is very important for controlling the pore size and pore structure of the membrane.12 Although it can downsize membrane pores and thus enhance membrane selectivity, this process often leads to the formation of pinholes and cracks within the membrane as well as an energy cost.13 
Therefore, there is a growing need to develop a facile and economical method to fabricate inorganic nanofibrous membranes with good selectivity and permeability. Graphene and its derivatives are promising candidates for potential applications in nanoelectronics, nanomedicine, supercapacitors and nanosensors due to their exceptional electronic, thermal, mechanical and optical properties.14,15 Current progress shows that free-standing graphene oxide (GO) paper can be formed by flow-directed assembly of individual graphene oxide sheets, since a stable suspension of GO can be obtained with the assistance of ultrasonic treatment.16,17 Although the GO paper exhibits excellent flexibility and high mechanical strength, it is not suitable for water filtration due to its poor permeability to fluids.16 